Infer line numbers in for the common case of found_line_eq().

Reverse the args so line number can be optional. We aren't adding a similar capability to found_lines_eq() at the moment, as I'm not yet sure how to make line numbers optional there without making things slightly unobvious.
Merge branch 'master' of https://github.com/mozilla/dxr into no-implicit-wildcards
Account for change to expected parameters for found_lines_eq.
Fix typo.